The goal of this research is to use daily diary methods to link stress and social interactions to mood, self-care behaviors, and blood glucose levels among adolescents (ages 14-16) with Type 1 diabetes. Previous research has relied on retrospective reports of stress rather than on-line measures. Eighty-eight adolescents (44 male, 44 female) will carry palm pilots for two separate 48-hour periods, which will prompt them every two hours during the day to complete a 2-minute questionnaire. The questionnaire will assess mood, stress, social interactions (conflict, social barriers), and self-care behaviors. Four prompts will also request that blood glucose levels are tested and recorded. Adolescents will wear the Actical, an accelerometer that measures frequency, duration, and intensity of movement during the same days of assessment. With this methodology, we can link stress and aspects of social interactions to mood, specific self-care behaviors, and blood glucose in a moment-to-moment fashion. A second goal of the study is to examine whether individual difference variables moderate these relations. We will examine whether sex influences these relations, as interpersonal stress is associated with more negative health consequences for females than males. We also will examine whether unmitigated communion (focus on others to exclusion of self) influences these relations, as relationship stressors and social barriers to self-care behavior may be more strongly tied to negative outcomes for people high in unmitigated communion.